Trim the beef brisket point of hard surface fat and silverskin, leaving a 0.25-inch fat cap; square the edges for even cooking.
Brush all sides with a thin coat of yellow mustard to help the seasoning adhere.
In a bowl, mix kosher salt, black pepper, paprika, garlic powder, onion powder, chili powder, and cayenne pepper to make a rub; reserve 2 tbsp rub for later.
Heat your smoker to 250°F with clean, steady smoke (hickory or oak are classic). Place the brisket on the grate with good airflow.
Smoke until the bark is set and the internal temperature reaches 170–175°F, 5–7 hours; after the first 2 hours, spritz the surface every 60–90 minutes with apple juice and water.
Wrap tightly in unwaxed butcher paper (or heavy foil) and return to the smoker. Continue cooking until 195–200°F and the meat feels probe-tender with little resistance, 2–3 hours more.
Meanwhile, make the sauce: combine ketchup, apple cider vinegar, molasses, honey, Worcestershire sauce, Dijon mustard, and garlic in a small saucepan; simmer over low heat, stirring occasionally, until glossy and slightly thickened, 10–15 minutes. Cool to warm.
Rest the wrapped brisket 30 minutes. Unwrap over a pan to catch juices.
Cube the point into 1.5-inch pieces. Toss the cubes with 0.5 cup of the sauce and the reserved rub in a disposable pan, adding any captured juices.
Return the pan to the smoker at 275°F, uncovered, and cook 45–90 minutes, stirring every 20 minutes, until the edges are caramelized and the cubes are tender and sticky; brush with a little more sauce and cook 5–10 minutes to set the glaze.